a word having grammatical function but assuming the meaning of an antecedent word or phrase for which it substitutes
the word "does" is a pro-form for "understands Greek" in "I can't understand Greekbut he does"
pro-form in American English
(ˈprouˌfɔrm)
noun
Grammar
a word used to replace or substitute for a word, phrase, or clause belonging to a given grammatical class, as a pronoun used to replace a noun or noun phrase, there used to replace an adverb or adverbial phrase of place, as in I parked the car near the entrance and left it there, or so used to substitute for a clause, as in Have they come? I think so
Word origin
[1960–65]This word is first recorded in the period 1960–65. Other words that entered Englishat around the same time include: bicycle kick, deinstitutionalize, disco, go-go, proxemics